電感是開關電源中常用(yong)(yong)的(de)(de)元件由于電(dian)(dian)(dian)(dian)流(liu)(liu)電(dian)(dian)(dian)(dian)壓(ya)(ya)相位不同(tong)，理論上沒有損耗(hao)。電(dian)(dian)(dian)(dian)感為(wei)儲能(neng)元件，與電(dian)(dian)(dian)(dian)容(rong)一起用(yong)(yong)在(zai)輸(shu)入濾波和輸(shu)出濾波電(dian)(dian)(dian)(dian)路上用(yong)(yong)來平滑電(dian)(dian)(dian)(dian)流(liu)(liu)。電(dian)(dian)(dian)(dian)感也(ye)被(bei)稱為(wei)扼流(liu)(liu)圈特點(dian)是(shi)流(liu)(liu)過(guo)其上的(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)有“很(hen)大(da)的(de)(de)慣性(xing)”。換句話(hua)說由于磁通連續(xu)特性(xing)，電(dian)(dian)(dian)(dian)感上的(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)必須連續(xu)否(fou)則會(hui)產生很(hen)大(da)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)尖峰(feng)（感性(xing)元件，如果突(tu)然斷(duan)電(dian)(dian)(dian)(dian)（電(dian)(dian)(dian)(dian)流(liu)(liu)回路被(bei)切斷(duan)），會(hui)產生很(hen)大(da)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)尖峰(feng)脈沖損壞與之串(chuan)聯的(de)(de)器件，此時必須加(jia)續(xu)流(liu)(liu)二極管(guan)續(xu)流(liu)(liu)！！！）。

　　電感常被理解為開關電源輸出端中的LC濾波電路中的L（C是其中的輸出電容）。雖這樣理解是正確的，為了理解電感的設計必須深入的了解電感的行為。在降壓轉換中，電感的一端連接到DC輸出電壓另一端通過開關頻率切換連接到輸入電壓或GND。
　　Buck/Boost型開關電源隨開關管的開關，儲能電感的電流波形等價于直流IDC上加一個I(P-P)值為ΔI的交流。因而IDC成為輸出電流IO主要消耗在負載上；交流ΔI消耗在負載電容的ESR（EquationSerial Resistance）上成為輸出紋波Vripple。
　　所以紋波(bo)電(dian)(dian)(dian)(dian)流(liu)(liu)的大(da)小同樣會(hui)影響(xiang)電(dian)(dian)(dian)(dian)感器和輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)容的尺寸(cun)紋波(bo)電(dian)(dian)(dian)(dian)流(liu)(liu)一般設定為最大(da)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)10%～30，因此對于降(jiang)壓(ya)型電(dian)(dian)(dian)(dian)源來(lai)說流(liu)(liu)過(guo)電(dian)(dian)(dian)(dian)感的電(dian)(dian)(dian)(dian)流(liu)(liu)峰值比電(dian)(dian)(dian)(dian)源輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)大(da)5%～15%之間。